Up to now, a lane keeping control for suppressing a deviation of a vehicle from a traveling lane is performed in a vehicle (for example, refer to Patent Literature 1). In the lane keeping control, an image ahead of the vehicle in a traveling direction is captured by an on-board camera to recognize a lane line or the like drawn along the traveling lane. When the vehicle attempts to cross the lane line, attention is paid to the driver by a warning or the like, and the vehicle is restrained from deviating from the traveling lane. Furthermore, in the lane keeping control, with the execution of the brake control and the steering control, a vehicle motion control for generating a moment in a direction of returning the vehicle in the traveling lane is performed while suppressing the deviation of the vehicle from the traveling lane, to thereby support the driver. The control improves the safety of the vehicle travel.
When the lane keeping control is executed, a design assuming a specific road surface condition or a road surface friction coefficient (hereinafter referred to as “road surface μ”), for example, a design on the assumption of a smooth road surface such as a dry road surface and an asphalt road surface is carried out. Originally, it is conceivable to preferably detect a road surface condition of the current traveling road surface of the vehicle and the road surface μ and execute the lane keeping control based on the detection result. However, because the road surface condition and the road surface μ cannot be accurately detected, the design is carried out on the assumption of a specific road surface condition or a road surface μ.